A multiprocessor environment can include a shared memory including shared lines of cache. In such a system, a single line of cache may be used or modified by one processor in the multiprocessor system. In the event a second processor desires to use that same line of cache, the possibility exists for contention. Ownership and control of the specific line of cache is preferably managed so that different sets of data for the same line of cache do not appear in different processors at the same time. It is therefore desirable to have a coherent management system for cache in a shared cache multiprocessor environment.
Within a coherent management system for cache in a shared cache multiprocessor environment, various mechanisms may be used to determine when a cache line is to be evicted from the cache memory in order to permit another cache line to be stored in the cache memory in place of the evicted line. Certain problems may exist in these mechanisms that may be improved with the use of the present invention. The present invention addresses the aforementioned needs and solves them with additional advantages as expressed herein.